Models J47-GE-17B and -33 were turbojet engines with exhaust reheat. Each engine had eight through-flow combustion chambers and incorporated a 12-stage axial flow compressor directly coupled to a single stage impulse turbine. The afterburner and variable nozzle were cantilevered from the turbine casing such that the whole unit was self supporting. Both engines were equipped with an accessory support located at the front.

Major Components and Their Function (Fig. 1.01)

Fig. 1.01. J47 Major Components

The auxiliary accessory drive, commonly referred to as the "power take-off" (PTO), consists of the auxiliary drive gear housing, auxiliary drive gears, supporting legs, and cowling. The gear box front face had four pads for mounting and driving two generators and two hydraulic pumps. Power was supplied to the entire auxiliary drive through a drive shaft joined by a spline to the compressor rotor. Four legs connecting the auxiliary gear case to the forward frame to formed a rigid support. Two cowling sections completely enclosed the engine-driven accessories space between the auxiliary drive gear case and forward frame; this also formed the inlet air guide inner shell.

The air guide and compressor front frames consists of island covers, air guide sectors, island fairings, and a set of retractable inlet screens. This section guides air into the compressor inlet. The island covers were used as junction points for fuel, lube, anti-icing, and certain electrical connections. The connecting lines were brought through the inlet air stream by passing through four streamlined fairings, one for each island. The four air guide sectors were located between the island covers to form the inlet air guide outer shell.

The compressor front frame included the accessory drive mechanism, No. 1 bearing support, inlet guide vanes, and the balance piston chamber. The frame consisted of an inner and outer section connected by eight streamlined struts to form an annular air inlet passage. Support for the drive gears, shaft housings, No. 1 bearing housing, and allied parts was provided by the inner section. The inlet guide vanes, made up of hollow blades mounted between two concentric rings, were attached to the frames inner section rear side along with an oil and air seal assembly. An air seal acted along the first stage compressor rotor wheel edge. Another seal acted near the compressor rotor hub. The area between these two seals formed a chamber, called the balance piston chamber, which was supplied with twelfth compressor stage air through the hollow inlet guide vanes. This air, acting against the compressor rotor forward end counteracted some of the rotor's forward thrust. The compressor front frame contained four engine mount pads, two on the horizontal and two on the vertical center line.

The compressor section was composed of the compressor rotor, stator, and compressor rear frame. The twelve-stage axial-flow compressor discharged air at a total pressure of approximately five atmospheres. The compressor rotor was the curvic coupling type, consisting of twelve wheels, each wheel having forged stainless steel compressor blades dove-tailed into its outer ring. The first nine wheels were aluminum alloy and the last three steel alloy. The compressor stator was a split cylindrical aluminum casing into which thirteen blade rows were dove-tailed. The casing exterior provided a convenient mount for many engine accessories.

The compressor rear frame supported the compressor stator at its forward face, the combustion chambers at its rear face, and the No. 2 bearing at its center. The turbine frame bolted to the compressor rear frame rear face to support the engine forward part. Equally spaced around the compressor rear frame shell were eight diffuser passages through which twelfth compressor stage air flowed to the combustion chambers. The eight duplex fuel nozzles were mounted on pads and extended directly into the diffuser passages with their tips extending into the inner combustion chambers.

The turbine section consisted of the eight combustion chambers, turbine frame, turbine casing, nozzle diaphragm, turbine wheel, and turbine shroud. Each direct flow combustion chamber consisted of a double-walled cylindrical assembly attached to the compressor rear frame and turbine frame by via quick disconnect clamps. Air from the compressor entering the combustion chambers passed into the annular spaces between the outer casings and the inner liners, and from there through perforations into the inner liners where it was mixed with the fuel sprayed from the nozzles and burned. Once ignition was achieved during the starting process combustion was continuous. The combustion chambers were interconnected by cross-firing tubes, which made it possible to start all burners using spark plugs in only two chambers. Hot gases leaving the combustion chambers passed through transition liners and through the stationary nozzle diaphragm to impinge upon the turbine wheel buckets where sufficient energy was extracted from the gases to drive the compressor and accessories.

The exhaust section consisted of a diffuser, burning section, and variable area jet nozzle. Immediately after the turbine wheel, the exhaust gases were decelerated in a diffusing section formed by the inner cone and outer pipe. Two circumferential spray-bar rows projected out radially from the inner cone, injecting fuel into the gas stream, which was ignited by a hot streak ignition system. A short distance downstream of this point, a double-V shaped flame holder was located to help sustain the burning process. An automatically controlled clamshell variable nozzle at the tailpipe end provided the correct nozzle conditions for optimum performance, with or without reheat.